The indices of lung ventilation and biomechanics of breathing were determined in 48 patients with chronic obstructive bronchitis (COB) aged 60-79 and 45 healthy subjects of the same age. Inpatients with COB a rise of lung ventilation, work of breathing, ventilation equivalent, positive reaction to oxygen, a decrease of maximal breathing capacity and reserve of breathing take place that reflect excessive and uneffective ventilation, limitation of its functional performance. These specific features are due to an increase in the total lung capacity at the expense of residual volume against a decrease of vital capacity with diminution of alveolar ventilation to lung ventilation ratio. But of decisive significance was disturbance of bronchial patency manifesting in a decrease of Tiffeneau index, midexpiratory flow, respiratory flows in forced respiration, especially in expiratory phase, concavity of flow-volume curve to volume axis, a rise of bronchial resistance.